I think you should mention the country you are talking about. In some counties what you said is not true. And different countries have different reasons (follow the trend, resource problem, past coups etc.).
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Apoorv KhurasiaMay 24 '12 at 1:53

4 Answers
4

I do not know which country do you mean but I suppose that in most countries the head of state is guerded by special services, and not police, not the army. The ceremonial escort though may be by some special military units, but the actual protection do the special services.

Piggybacking on what mgb said, it is necessary from a security standpoint that heads of state have a dedicated security force whose sole purpose is the protection of the head of state. Local police forces, or even national police forces, have conflicting agendas that can lower their focus. That said, the Secret Service (in the US) and their counterparts in other countries work with local security whenever the head of state travels.

Note that in the USA, the people responsible for the President's security are The Secret Service. They are not military.

They can be viewed as a kind of Federal-level police. They used to be under the Treasury Department (with the IRS and the folks who make our money), rather than the FBI or Justice Department. In 2003 they got moved into the new Department of Homeland Security (along with a mishmash of other domestic security-related agencies that weren't politically powerfull enough to prevent it).

@quant_dev - Mostly historical accident. You are not alone in finding that odd.
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T.E.D.♦Jul 16 '12 at 17:38

@quant_dev - ...however, that appears to have changed in 2003 in the wake of 9/11. I'll fix the answer. They still aren't under the FBI like you might expect though. The DHS they are under now is even more of a creature of historical accident, so perhaps it is appropriate in a way. :-)
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T.E.D.♦Jul 16 '12 at 17:41

@quant_dev: Because the primary purpose of the Secret Service was to combat counterfeiting. That it also provided security to politicians is, as TED said, historical accident.
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CharlesJul 18 '12 at 16:57

In addition to the answers posted, a couple of common-sense answers come to mind. First, police aren't specifically trained for that job -- a head of state needs bodyguards, not law-enforcement officers. Second, police serve a city or other locality. A head of state would want one set of guards who traveled with them, rather than having a different set everyplace they went.